Abstract
The internal elastic lamina (IEL) serves as a barrier for cells and
macromolecules between the intima and media in the vascular wall. We evaluated
the morphological changes and quantitative assessments of the IEL architecture
in the coronary circulation of pigs fed with a high cholesterol diet.
Transmission electron microscopy (TEM) analysis of the IEL from
hypercholesterolemic coronary arteries revealed fragmentation of the IEL
associated with a decrease in the thickness. Confocal microscopy and scanning
electron microscopy (SEM) revealed an altered pattern characterized by a large
oval fenestration in the IEL of hypercholesterolemic vessels. Morphometric
analysis of confocal microscopy images demonstrated that the IEL of
cholesterol-fed animals were characterized by an increase in the minor diameter
of the fenestrae (2.16±0.04 µm vs 3.32±0.06 µm, p=0.003) and a
decrease in the fenestrae density (22,333±1,334/mm2 vs 17,552±931/mm2,
p=0.015) compared to controls. The percentage of the IEL area covered by the
fenestrae correlated with the intimal thickness (r=0.79, p=0.004). The
immunoreactivity for matrix metalloproteinase-3 (MMP-3) increased in
cholesterol-fed coronary arteries, predominantly in the neointima. This study
demonstrates experimental hypercholesterolemia induced ultrastructural changes
of the IEL in the coronary circulation. The IEL may play an important role in
the development of structural changes which characterize the early phase of
coronary atherosclerosis.